Have you considered dropping the Ninja side, and then grafting a spellcaster onto the other half of the Gestalt?
Slayer/Ninja is a nearly redundant Gestalt, with Ninja providing the least as far as the base chassis goes (Only +2 skills per level).
If you were a Cleric or Inquisitor of Shizuru, you'd get the Katana as her Favored Weapon, and Darkness/Deeper Darkness as available spells.
If you go Inquisitor, Sacred Huntmaster would give you the added bonus of a permanent flanking partner, so you don't need to rely on the Darkness all the time, since no matter what route you go it's a limited number of times per day.
Have you considered dropping the Ninja side, and then grafting a spellcaster onto the other half of the Gestalt?
Slayer/Ninja is a nearly redundant Gestalt, with Ninja providing the least as far as the base chassis goes (Only +2 skills per level).
If you were a Cleric or Inquisitor of Shizuru, you'd get the Katana as her Favored Weapon, and Darkness/Deeper Darkness as available spells.
If you go Inquisitor, Sacred Huntmaster would give you the added bonus of a permanent flanking partner, so you don't need to rely on the Darkness all the time, since no matter what route you go it's a limited number of times per day.
A Sacred Huntsmaster Inquisitor gestalted with a Slayer really may as well be a Ranger, wouldn't they? WIS based spellcasting, Full BAB, Animal Companion, etc. means a Ranger covers many of the same bases.
I would personally suggest a Kensai/Slayer. DEX + INT synergy, more than decent stealth/melee/spellcasting capability, and damage through the roof.
If you're allowed (don't see why not), you could also VMC Rogue to gain a few decent things any Kensai would love, as well as tons more "ninja" flavor.
Blinding Sneak Attack isn't much of a work-around anyway. It's a max of 3 times per day, has a Fort save to negate, and requires you to Sneak Attack them in an area of Darkness.
Which means you're already flanking (and thus the effect is largely pointless) or they already can't see in darkness (and thus the effect is ENTIRELY pointless).
Deeper Darkness, on the other hand, trumps Darkvision.
Have you considered running Shadowdancer? Or at least a dip?
With 2 levels for Hide in Plain Sight, Blinding Sneak Attack is unnecessary as well. Even if they can see through the darkness, you can hide in it.
If you go the Cleric/Inquisitor route, the Darkness Domain is largely pointless. Deeper Darkness is already on both lists, and the Domain abilities kinda suck.
You could also drop Slayer for Sanctified Slayer Inquisitor instead. The main issue there is the loss of Slayer Talents.
Since 3rd party stuff seems allowed, there's the Darkness Oracle Mystery for Cha synergy, HiPS and See in Darkness. And likewise Deeper Darkness as a spell known. There's a similar Shaman archetype by the same people.
Have you considered dropping the Ninja side, and then grafting a spellcaster onto the other half of the Gestalt?
Slayer/Ninja is a nearly redundant Gestalt, with Ninja providing the least as far as the base chassis goes (Only +2 skills per level).
If you were a Cleric or Inquisitor of Shizuru, you'd get the Katana as her Favored Weapon, and Darkness/Deeper Darkness as available spells.
If you go Inquisitor, Sacred Huntmaster would give you the added bonus of a permanent flanking partner, so you don't need to rely on the Darkness all the time, since no matter what route you go it's a limited number of times per day.
A Sacred Huntsmaster Inquisitor gestalted with a Slayer really may as well be a Ranger, wouldn't they? WIS based spellcasting, Full BAB, Animal Companion, etc. means a Ranger covers many of the same bases.
I would personally suggest a Kensai/Slayer. DEX + INT synergy, more than decent stealth/melee/spellcasting capability, and damage through the roof.
If you're allowed (don't see why not), you could also VMC Rogue to gain a few decent things any Kensai would love, as well as tons more "ninja" flavor.
Ranger may cover similar bases...but far less well. Studied Target is all around better than Favored Enemy, and the Inquisitor gets 6th level casting (trumps 4th), Bane (Amazing, and also better than FE), and a load of other, better class features than the Ranger.
His main advantage over the Inquisitor is full BaB and those sweet, sweet Combat Style feats...both of which the Slayer provides as well, on top of a less situational damage boost and access to some choice Rogue Talents.
Gestalting two full BaB classes is inadvisable. 3/4 BaB characters (especially 6th level casters) get a LOT of neat tricks for the lowered HD and BaB. Giving them full BaB on top of that is WOW, as opposed to just Ranger which is good, but not as excellent as full BaB, d10 HD, all Good saves (With Stalwart, and Evasion at Slayer 10 or so) Inquisitor.
True, having all good saves on top of Stalwart & Evasion is definitely a great thing to have. I personally like the Inquisitor + Unchained Monk combo myself.
If Sacred Huntsmaster archetype is chosen you can even go Chained Moonk with Sohei archetype for a powerful mounted build. You do lose out on BAB and HD though. Speaking of which, it can sometimes be quite useful to gestalt two classes of similar BAB, and besides the above mentioned 3/4 BAB one there is always the Paladin/Bloodrager, who can heal his own fatigue, gain tremendous health with Lay on Hands + Lesser Celestial Totem, and deals the most damage period with the ability to Rage AND Smite. Incredibly synergistic all around. Add to that the Sorcerer and the Wizard, who combined can make the best blaster caster in the world. Arcanist may or may not be included somewhere. And then my personal favorite, the Master Summoner + Skald. No explanation needed there, I'm sure.
But yeah back to the topic at hand, Kensai isn't a bad class to Gestalt with Slayer either. Still get 6th level Arcane casting, all good saves, and a ton of combat abilities, especially if you like critical hits. The arcane list is also quite the boon, as there are unfortunately a few holes in the Inquisitor spell list (lack of Fly being the most glaring). Despite the flak it recieves, the Magus has almost all the staple spells it needs to contribute to combat and the ability to poach whatever else it needs from the sorcerer/wizard list.
Really though, this just speaks back to the age old paradigm of Magus vs Inquisitor. Both are great classes, either is a good choice.
The main issue being that without changing classes, or relying on UMD...neither is really possible.
Though again remember for the Drow, Darkvision doesn't see through Deeper Darkness.
Ninja get Darkvision for 1 ki per hour.
EDIT: This concept also works with smoke/fire-sight, fog/water-sight.
Just remember, what you can see in your party may have issues with.
/cevah